Numerous geodetic surveying devices have been known since antiquity for measuring one or in particular a plurality of target points. The distance and direction or angle from a measuring device to the target point to be measured are recorded as spatial standard data and also in particular the absolute position of the measuring device is detected in addition to any existing reference points.
Generally known examples of such geodetic surveying devices are represented by theodolites, tachymeters, and total stations, which are also designated as electronic tachymeters or computer tachymeters. A geodetic measuring device of the prior art is described, for example, in published application EP 1 686 350. Such devices have electro-sensory angle and distance measuring functions, which permit a determination of the direction and distance to a selected target. The angle or distance dimensions are ascertained in the interior reference system of the device and must possibly still be linked to an external reference system for an absolute position determination.
In many geodetic applications, points are surveyed by placing specially designed target objects. These typically consist of a plumb stick having a targetable module, for example, a reflector for defining the measurement section or the measurement point. These target objects are targeted by means of a surveying device, a direction and a distance to the objects are determined, and a position of the objects is derived.
Similarly to this point measurement, marking of already known target points or of points, the position of which was defined prior to a marking procedure, can be performed. In contrast to the point measurement, in this case, the position or the coordinates of the points to be marked are known and are to be marked. For such a marking procedure, a plumb stick or a surveying rod is conventionally also used, which is guided by a user and positioned on a target point. For this purpose, the user can move toward the target position of the target point based on position information generated by the surveying device, wherein the surveying rod can be automatically targeted from the surveying device by a second person or by an automatic mechanism assigned to the surveying device. If the target point has been reached, the user can perform a marking of the point.
Modern surveying devices such as a total station for such marking and surveying tasks have microprocessors for digital further processing and storage of detected measurement data. The devices are typically produced in a compact and integrated construction, wherein coaxial distance and angle measuring elements and computer, control, and storage units are normally integrated in a device. Depending on the level of development of the total station, means for motorization of the target optics, for reflector-free route measurement, for automatic target search and tracking, and for remote control of the entire device are integrated.
Total stations known from the prior art also have a radio data interface for establishing a radio link to external peripheral components, for example, to a data acquisition device, which can be implemented in particular as a handheld data logger, remote control unit, field computer, notebook, small computer or PDA. By means of the data interface, it is possible to output measurement data acquired and stored by the total station for external further processing, to read in externally acquired measurement data for storage and/or further processing in the total station, to input or output remote control signals for the remote control of the total station or a further external component, in particular in mobile field use, and to transfer control software to the total station.
For aiming at or targeting the target point to be surveyed, geodetic surveying devices of this type have, for example, a telescopic sight, for example, an optical telescope, as a targeting unit. The telescopic sight is generally rotatable about a vertical standing axis and about a horizontal tilt axis relative to a base of the measuring device, so that the telescope can be aligned on the point to be surveyed by pivoting and tilting. Modern devices can have, in addition to the optical vision channel, a camera, which is integrated in the telescopic sight and is aligned coaxially or in parallel, for example, for acquiring an image, wherein the acquired image can be displayed in particular as a live image on the display screen of the display-control unit and/or on a display screen of the peripheral device used for the remote control—for example, of the data logger or the remote operation unit. The optic of the targeting unit can have a manual focus—for example, a set screw for changing the position of a focusing optic—or can have an autofocus, wherein the change of the focal position is performed, for example, by servomotors. Automatic focusing units for telescopic sights of geodetic devices are known, for example, from DE 197 107 22, DE 199 267 06, or DE 199 495 80.
The above-mentioned surveying systems and applications from the prior art share the feature that a position of a surveying device or a surveying rod is to be determined uniquely and with geodetic precision and this position is to be specified at least in an absolute coordinate system. For this purpose, a transformation of the respective measured position information from an inner measuring coordinate system into the absolute, higher-order coordinate system can be performed.
A position determination method having a coordinate transformation for points to be surveyed using a geodetic device is disclosed, for example, in US 2009/0082992. In principle, the intrinsic position of the geodetic device, i.e., the station coordinates of the measuring device, or the position of new points to be surveyed can be derived as a so-called free stationing from measurements with respect to known, fixed measurement points as reference points. This procedure is also designated as referencing of the measuring device position or the new points in relation to the measured and known positioned reference points. For this purpose, firstly the position of the known reference points relative to the viewpoint is calculated in a local coordinate system. With the aid of the known coordinates of the reference points, when the required number of measurements is provided, equalized transformation parameters are calculated, from which the station coordinates sought or the coordinates sought of the new points are derivable.
Furthermore, a target unit or a surveying rod provided with a target unit can be targeted by a stationary position determination unit, for example, a total station, and automatic guiding of a user or operator to a provided target point can be performed employing the image data recorded by the stationary position determination unit.
For this purpose, in U.S. Pat. No. 7,222,021 or corresponding EP 1 293 755, a surveying system, designated in this patent specification as an operator guiding system, is proposed having a stationary measuring unit (position determination unit), which is equipped with imaging means, for example, a camera, and a mobile station having the function of a mobile target unit, which is equipped with display means, for example, a display screen for displaying a current position of the user based on stored landscape images or data and current images, which are seen from the stationary measuring unit. Furthermore, it is disclosed how an operator can be guided to the target point by means of correlation between the current position data, which is measured from the stationary measuring station, including the camera image, for the mobile station, stored data having the provided position of the target point by marking on the display screen of the target unit, for example, by directional display by means of an arrow on the display screen.
Furthermore, positioning or guiding of a user to a previously known target position can be performed based on GNSS signals without the use of a surveying device. A surveying rod can have a GNSS receiver and a processing unit or a controller attachable to the surveying rod for determining position coordinates. By comparing the known target position to the respective position ascertained by the GNSS signals, the user can thus find the target point and perform possible marking there.
A further position determination method for determining a position of an optical geodetic device is known from WO 2009/039929. In this case, the position determination is performed using a mobile unit, which is equipped with a GNSS receiver, and a total station.
This method allows a linkage of a GNSS position determination to a position determination based on a geodetic device and also a usage linked thereto of the respective advantages of both methods. The condition for the method is that the unit moved, for example a work machine, has a position determination device such as a GNSS receiver, using which a position determination is possible at least at some points in time.
GNSS positions are then advantageously determined in real time as reference positions of the advancing work machine and relative positions of the reference point assigned to the work machine by means of the total station for known points in time. The GNSS positions relate to an external coordinate system and the relative positions relate to an internal coordinate system with respect to the total station. Both a GNSS position and also a relative position are at least partially determined for points in time which are identical or are close to one another with respect to time, wherein the positions corresponding with respect to time are each assigned to one another in pairs and therefore respectively form a position pair correlated with respect to time for one or two neighboring points in time.
From the correlations of the respective individual pairs, a balanced relationship can now be derived between external and internal reference systems, wherein this relationship is represented in particular by balanced transformation parameters. The derived balanced relationship specifies how the external reference system relates to the internal reference system with respect to the total station. On the basis of this relationship, for example, the coordinates of the relative positions measured using the total station or the position of the total station itself in the external reference system can be transformed and used for the position determination of the work machine in the external reference system.
A shared requirement for carrying out the above-mentioned method for determining positions is that a connection, e.g., for signal transmission, must be provided between the respective components used for the determination. In particular, for measuring a target point or a reflector arranged on a surveying rod, an optical contact must be provided between surveying device and the reflector, i.e., a measuring beam can be aligned directly without beam interruption on a corresponding target. Similarly thereto, for a position determination by means of GNSS signals, a connection must be able to be established between a GNSS receiver and a number of GNSS satellites for transmitting the signals. Therefore, in each case an interaction between at least two measuring components is the foundation of a reliable and executable position determination. This condition simultaneously forms a shared disadvantage of the methods. If the connection or contact line respectively required for the method is obstructed or interrupted in any way, a determination of the position cannot be performed. Such connection obstructions can be caused, for example, by buildings which are located in a linear connecting line, or rugged terrain, and can therefore prevent the execution of the position determination method.